There are several things to keep in mind when setting up your composting station.
Sun or shade?
A worm bin is best placed in the shade. The worms will not fare well in hot temperatures or during a deluge of water during a rainstorm. By placing them in the shade, they will be more protected from the elements and less likely to dry out. As for a regular compost bin, direct sunlight does not cause the compost pile to heat up. The microbes working busily inside the compost are why the pile heats up. With this in mind, keeping your compost bin in the shade will decrease water evaporation. Also, people are more likely to turn their pile if they do not have to go out into the hot sun to do it.
Dirt or cement?
For a compost bin, it is best if it is placed on the dirt. This allows the beneficial insects to crawl up into the bin. These insects will speed up the decomposition process and are naturally occur in a healthy compost pile. Put hardware cloth or wire mesh underneath the compost bin to prevent the larger animals from digging underneath and into the bin. If a compost pile is set on cement, it is likely that the cement will be stained. For a worm bin, it does not matter if it is placed on cement or on dirt. It is more important that the bin is in the shade. People often even keep worm bins inside their garage, under their counter, or in a closet.
How close do I want my compost bin to the house?
Most people do not want to put their compost bin directly up against their house because of smell and pest attraction fears. If you are composting correctly, neither of these problems should be of issue. How close you put your bin to your house should more so be determined by hose length (if your bin is further away than your hose is long, you'll be lugging buckets over to your pile!) and ease of use. If you don't see yourself hoofing it across the yard to dump out your kitchen scraps, then you probably shouldn't put your bin all the way across your yard. As for the pests and smells, err on the side of caution. If something goes wrong in your pile and it starts to smell or you get an unwanted visitor, it's better away from your house than directly under your kitchen window.
How much room will my compost bin need?
If you plan on being an active composter and turning your compost pile, it is important that you have a space twice the size of your compost bin. This allows you to turn and then rebuild your bin directly next to where it was previously sitting. Turing your bin increases air flow and allows the microbes to break down the material more quickly. If you plan on having a more passive bin, this is obviously not necessary, though you probably want a little room around the bin so it can be accessed from all angles. Worm bins, on the other hand, do not need extra space.